Objective-C - if 语句

if 语句由一个布尔表达式和一个或多个语句组成。

语法

Objective-C 编程语言中 if 语句的语法是 −

if(boolean_expression) {
   /* statement(s) will execute if the boolean expression is true */
}

If the boolean expression evaluates to true, then the block of code inside the if statement will be executed. If boolean expression evaluates to false, then the first set of code after the end of the if statement (after the closing curly brace) will be executed.

Objective-C programming language assumes any non-zero and non-null values as true, and if it is either zero or null, then it is assumed as false value.

流程图

示例

#import <Foundation/Foundation.h>
 
int main () {
   
   /* local variable definition */
   int a = 10;
 
   /* check the boolean condition using if statement */
   if( a < 20 ) {
      /* if condition is true then print the following */
      NSLog(@"a is less than 20\n" );
   }
   
   NSLog(@"value of a is : %d\n", a);
   return 0;
}

当上面的代码被编译和执行时，会产生如下结果 −

2013-09-07 22:07:00.845 demo[13573] a is less than 20
2013-09-07 22:07:00.845 demo[13573] value of a is : 10